a) Field of the Invention
The present invention relates to a conductive polysulfone resin composition which has improved electrical conductivity and is excellent in heat resistance, processability and mechanical strength, and a high-heat-resistant, conductive semi-conductor article molded from the composition.
b) Description of the Related Art
As a technique for providing electrical conductivity to an aromatic polysulfone resin, it has been disclosed, for example, in Japanese Laid-Open Patent 61670 (1978) a process for preparing an electrically conductive composite by the addition of conductive materials such as conductive carbon to the aromatic polysulfone resin. The invention describes that a composite having an electrical resistance of 10.sup.10 .OMEGA. or less can be prepared. In practice, however, the semi-conductor material thus obtained has a resistance of 10.sup.7 -10.sup.10 .OMEGA.. According to the information of the present inventors, a formulation of conductive carbon for providing conductivity to the aromatic polysulfone resin causes an increase in melt viscosity corresponding to the amount of addition. Consequently, kneading and molding of the molten composition becomes difficult or impossible in a formulating region capable of providing sufficient conductivity.
On the other hand, an injection molding resin composition containing conductive carbon dispersed in a polyphenylene sulfide resin has been known. Japanese Laid-Open Patent 8335 (1985) and 81450 (1987) disclose compositions containing conductive carbon having high oil absorption. However, the specific polyphenylene sulfide resin employed in the former patent is difficult to obtain uniform dispersion of conductive carbon and is not effective for furnishing electrical conductivity. Consequently, a remarkably increased amount of conductive carbon must be added in some uses. On the other hand, the latter patent describes that the amount of conductive carbon added can be decreased by using a polyphenylene sulfide resin having lower viscosity than that of the resin in the former patent. The latter patent, however, illustrates that the effect on conductivity improvement indicated by resistance is only 10.sup.1 .OMEGA. or at most 10.sup.2 .OMEGA., value which is smaller than the addition effect of conventional conductive carbon.
Japanese Laid-Open Patent 98632.(1983) discloses a molding resin composition containing 100 parts by weight of a resin blend composed of 99 to 50% by weight of an aromatic polysulfone resin and 1 to 50% by weight of a polyphenylene sulfide resin and from 10 to 200 parts by weight, most preferably from 80 to 180 parts by weight of a filler. The filler which can be employed in the invention includes, for example, reinforcements such as glass fibers and carbon fibers, impact strength improvers such as graphite, heat resistance improvers such as antimony trioxide, electrical property improvers such as clay and mica, acid resistance improvers such as barium sulfate, and thermal conductivity improvers such as iron. Practical cases described in the examples are only the use of glass fiber or carbon fiber alone and the combined use of 80 parts of carbon fiber and 20 parts of graphite. No consideration is taken in the invention on the solution of a specific problem related to processing methods such as injection molding. Further, no disclosure is found at all on providing a molded article having excellent electrical conductivity.
Accompanied by high density packaging of electronic equipment, semi-conductors are mounted on a through-hole substrate in order to increase density. When moisture is adsorbed on semi-conductor parts, water vapor generates in the interior of the semi-conductor parts by heating with flow solder, leads to blistering or cracking and damages the semi-conductor. As a countermeasure, it has been required in the mounting to furnish a step for previously drying the semi-conductor at temperature of above 100.degree. C to remove moisture. Conventionally, the semi-conductor drying step is carried out after once transferring the semi-conductor from a tray of conductive vinyl chloride resin or styrene base resin to a die-cast aluminum tray. The dried semi-conductor is delivered after transferring again to the above resin tray. Thus a complex step has been required. In order to simplify the step and to replace the expensive die-cast aluminum tray, application of a resin tray having excellent heat resistance is now under investigation.
Another mounting technique of the semi-conductor is a packaging method using tape automated bonding (TAB) in order to meet the demand for increased density and reduction in thickness. Application of resin parts called "carrier" is also under investigation for the transfer of the semi-conductor.
A heat resistant carrier composed of polypropylene resin has been used as a resin carrier having heat resistance of above 100.degree. C. which is suitable for the object. Drying temperature is, however, liable to increase in order to reduce drying time of the semi-conductor. Drying is carried out at 130.degree.to 150.degree. C., sometimes at a high temperature of 175.degree. C. Such a high temperature causes defective phenomena such as warpage and deformation and makes the semi-conductor useless. Nylon resin is also used due to higher heat resistance than polypropylene resin. A carrier composed of nylon resin has a high heat-shrinkage and leads to problems such as dimensional change of the carrier which renders automatic transfer with a robot impossible. Polyphenylene sulfide is a resin having a high heat resistance. Molding of carriers composed of the resin has, however, a problem of so-called "flash" known to those who are skilled in the art. Flash is a problem of generating on a molded article a surplus portion formed by squeezing-out and solidifying the resin through a parting line of the mold.